Engineered Grade Rafter Ties (Roof) lumber is engineered wood framing material meeting ANSI/APA grading standards for structural reliability and dimensional consistency. Moisture content is controlled to 19% or less, ensuring dimensional stability and resistance to warping. Allowable stress values are established through extensive testing programs, with each grade representing minimum guaranteed strength properties.
Spruce-Pine-Fir (SPF) offers balanced strength and economics, making it the preferred choice for residential construction across North America.
Applications include floor joists, roof trusses, wall studs, and structural beams in residential and light commercial construction. Grading stamps confirm species, grade, moisture content, mill identification, and applicable grading rules. Connections utilize galvanized fasteners, joist hangers, and metal connectors ensuring load transfer without damage to wood fibers.
Design values are published in the National Design Specification (NDS) for wood construction, with adjustments for duration of load, moisture content, temperature, and other factors. Untreated lumber is suitable for protected interior environments, while pressure-treated lumber provides extended service life for exterior exposure or ground contact.
Sustainability benefits include rapid growth rates, renewable production, and lower embodied carbon compared to concrete and steel. Long-term durability depends on adequate ventilation, moisture control, and pest resistance measures. Cost reflects species selection, grade requirements, and market availability.